Automated fiber placement (AFP) is often used to construct composite components due to the superior mechanical properties obtained from improved fiber orientation control and fiber architecture compared to laying up fiber by hand. However, AFP has high ancillary costs related to preparing feedstock material to be compatible with AFP machinery. For example, AFP requires several value-added steps such as pre-impregnation, B-staging, refrigerated storing and shipping, slitting, and respooling. The material and preparation costs are a significant portion of the total cost of fabricating a composite component via AFP. Furthermore, these preparations are not always performed by the same organization or at the same location, resulting in additional shipping costs and diminished shelf life and out-life.
Composite parts also suffer from a number of defects whether they are formed via AFP or by hand. For example, laminate porosity is a common defect in which air is trapped between plies of pre-impregnated material. Substantial pressure must be applied to the laminate in order to compress or discharge the air to the laminate's edge.
Pre-impregnated materials also have a very high surface area to mass ratio, and any atmospheric contact inherent to handling, shipping, slitting, thawing, and layup provides opportunity for the resin to absorb moisture from the air. This moisture can boil during elevated temperature cures, thereby forming porosity in the composite part.
Solvent is often used to aid in pre-impregnation processes and is frequently not completely removed before layup. Residual solvent can boil during laminating or curing, thereby forming voids in the composite part.